To clarify my "why", I understand the technical reason (I have my browser set to proper British English and it's grabbing the currency character from there) but I don't understand why the Blockbuster site is configured to do that, as opposed to always using a $.

Most likely because they use the same platform for their regional websites (Blockbuster used to have a presence here, for example) so they just wrote internationalisation into it from the start so they didn't have to later.

In terms of why you saw the ad, it is indeed because they use AdSense to fill quota - if you look at the UTM parameters on the Blockbuster site when you click the ad it kind of gives it away. Blockbuster, however, should be given a swift kick for failing to correctly target their campaign however, as there is a section in AdWords campaign manager allowing you to target to markets you actually operate in.

Kyanar: Most likely because they use the same platform for their regional websites (Blockbuster used to have a presence here, for example) so they just wrote internationalisation into it from the start so they didn't have to later.

But even then it should be using geolocation rather than the language settings; for example an English speaker in Europe would still want to see prices in euros, not dollars.

Kyanar: Most likely because they use the same platform for their regional websites (Blockbuster used to have a presence here, for example) so they just wrote internationalisation into it from the start so they didn't have to later.

In terms of why you saw the ad, it is indeed because they use AdSense to fill quota - if you look at the UTM parameters on the Blockbuster site when you click the ad it kind of gives it away. Blockbuster, however, should be given a swift kick for failing to correctly target their campaign however, as there is a section in AdWords campaign manager allowing you to target to markets you actually operate in.